This invention relates to the formation of a hard, wear-resistant surface on a gamma titanium aluminide alloy.
Titanium aluminides are a class of alloys whose compositions include at least titanium and aluminum, and typically some additional alloying elements such as chromium, niobium, vanadium, tantalum, manganese, or and/boron. The gamma titanium aluminides are based on the gamma phase found at nearly the equiatomic composition, with roughly 50 atomic percent each of titanium and aluminum, or slightly reduced amounts to permit the incorporation of other alloying elements. The titanium aluminides, and particularly the gamma titanium aluminides, have the advantages of low density, good low and intermediate temperature strength and cyclic deformation resistance, and good environmental resistance.
Gamma titanium aluminides can be used in aircraft engines. They potentially have applications such as low-pressure turbine blades and vanes, bearing supports, compressor casings, high pressure and low pressure hangars, frames, and low pressure turbine brush seal supports. They may also have application in other products such as automotive valves and superchargers.
The gamma titanium aluminides are not noted as having a high resistance to erosion damage. For some applications of gamma titanium aluminides, the inventor has recognized that it would be desirable to provide a hardfacing on the gamma titanium aluminide component substrate. Available hardfacing materials, however, are chemically and/or physically not compatible with the gamma titanium aluminides. Hardfacing materials based upon iron, cobalt, or nickel alloys chemically react and interdiffuse with the titanium to form undesirable reaction products such as brittle intermetallic phases, they are dense, thereby adding unnecessarily to the weight of the hardfaced component, and they have significantly different thermal expansion coefficients, leading to separation of the hardfacing from the substrate during service. Those hardfacing alloys based upon titanium compositions have insufficient thermal resistance and performance at elevated temperatures, and also have different thermal expansion coefficients.
There is, accordingly, a need for an improved approach to the hardfacing of gamma titanium aluminides. The present invention fulfills this need, and further provides related advantages.